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electrical:depth_of_discharge [2023/08/17 21:22]
frater_secessus [knowing when SoC is 100% (fully charged)] 		electrical:depth_of_discharge [2023/08/17 21:34]
frater_secessus [Depth of discharge / State of Charge]
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 DoD is the inverse of //State of Charge (SoC)//.  Example:  a battery at 30% DoD is at 70% SoC. DoD is the inverse of //State of Charge (SoC)//.  Example:  a battery at 30% DoD is at 70% SoC.
- 
-DoD has a **significant impact on longevity of lead deep cycle batteries**.((and, to a lesser degree, lithium batteries))  For this reason [[electrical:inverter|Inverters]] and other high-load devices may have a [[electrical:12v:lvd|low voltage cutoff]] to prevent going below a given SoC, typically 50%.   
  
 Note: This information is primarily relevant to lead-chemistry batteries.  Lithium batteries have [[#lithium_soc|different DoD capabilities and lifecycles]]. Note: This information is primarily relevant to lead-chemistry batteries.  Lithium batteries have [[#lithium_soc|different DoD capabilities and lifecycles]].
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 So for a 225Ah Trojan T-105 that might be when current acceptance drops to **4.5A at 14.8v**.  Some solar charge controllers have a setting for defining the final current acceptance ("trailing amps", "endAmps").  Usually humans observe system behavior and set an Absorption duration likely to terminate at about the correct time.((later typically better than earlier with lead)) So for a 225Ah Trojan T-105 that might be when current acceptance drops to **4.5A at 14.8v**.  Some solar charge controllers have a setting for defining the final current acceptance ("trailing amps", "endAmps").  Usually humans observe system behavior and set an Absorption duration likely to terminate at about the correct time.((later typically better than earlier with lead))
 +
 +Mythbusting:  although it is a common saying, a lead battery is not reliably 80% SoC when Absorption voltage is reached.  See [[opinion:frater_secessus:charging_faster|this article]] for why this is so. 
 +
  
 With **lithium batteries** humans might use use amp-counting with [[electrical:12v:battery_monitor|a battery monitor]] but most charge controllers don't talk to battery monitors.  So we can take one of two major approaches: With **lithium batteries** humans might use use amp-counting with [[electrical:12v:battery_monitor|a battery monitor]] but most charge controllers don't talk to battery monitors.  So we can take one of two major approaches:
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-Solar is typically a moderate (or "soft") charging source so the guidelines above are probably close enough to start from.  Alternator charging from combiner or large DC-DC may be high ("firm") enough for SoC estimates to be artificially high.  +Solar is typically a moderate (or "soft") charging source so the guidelines above are probably close enough to start from.  Alternator charging from [[electrical:12v:directcharginglfp|combiner]] or large [[electrical:12v:b2b|DC-DC]] may be high ("firm") enough for SoC estimates to be artificially high.   
 + 
 +So while we can say with confidence that a 100Ah Li battery charged at 20A to 14.0v will be ~100% SoC, the same battery charged to 14.0v at 80A might only be at 75% SoC.  And it **could get damagingly overcharged** if charged to 14.0v very gently at something like 5A.((the BMS cannot detect this scenario))
  
-So while we can say with confidence that a 100Ah Li battery charged at 20A to 14.0v will be ~100% SoC, the same battery charged to 14.0v at 80A might only be at 75% SoC.  The amp counter will probably help here during charging. +The amp counter will probably help here during charging although even it can be thrown off;  see the battery monitor article for more on this. 
  
  
electrical/depth_of_discharge.txt · Last modified: 2023/08/17 21:36 by frater_secessus

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